Cast Alloy

ABSTRACT

The casting alloy according to the invention is based on aluminum-iron-nickel and includes the following elements: 
     
       
         
               
               
               
             
                   
                   
               
                   
                 iron 
                 0.8 to 3.0% by weight 
               
                   
                 nickel 
                 0.1 to 3.5% by weight 
               
                   
                 boron 
                 40 to 300 ppm 
               
                   
                 zinc 
                 0-5% by weight 
               
                   
                 tin 
                 0-5% by weight 
               
                   
                 copper 
                 0-3% by weight 
               
                   
                 manganese 
                 0-1% by weight 
               
                   
                 magnesium 
                 0-0.6% by weight 
               
                   
                 phosphorus 
                 0-500 ppm 
               
                   
                 Silicon 
                 0-0.4%.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority to European Patent Application No. 21188809.4, filed on Jul. 30, 2021, the disclosure of which is hereby incorporated by reference in its entirety.

BACKGROUND OF THE INVENTION Field of the Invention

The present invention relates to a casting alloy based on aluminum, iron and nickel with the addition of boron. Further the invention relates to the use of the alloy for high pressure die casting or gravity die casting. The alloy according to the invention is used for the production of rotors and stators for electric motors and heat ex-changers, cooling and heating elements in the electronics sector or in vehicle construction.

DESCRIPTION OF RELATED ART

The use of Rotor-Aluminum (e.g. in qualities of 99.7% Al) in high pressure die casting has been known for a long time. Typically, a metallic body is placed in the die-casting mold and the aluminum rotor or stator is cast into this metallic body. In this way, difficulties that arise when casting such an alloy are avoided, above all the high tendency to stick to steel, which otherwise leads to rapid wear of the casting mold. Other typical disadvantages are high shrinkage, very high casting temperatures, poor mechanical machinability and particularly low strength (e.g. Rpo.2 of 20-40 MPa for the alloy A199.7E).

For heat exchangers produced via high pressure die casting, alloys of the AlSi type are often used, e.g., the alloy AlSigSr (Castasil-21). Compared to Rotor-Aluminum, these alloy type is better castable. The tendency to stick to the casting mold, shrinkage, mold fillability and casting temperatures are more advantageous. However, the lower electric and thermal conductivity compared to Rotor-Aluminum are disadvantageous. With the help of a heat treatment, an electric conductivity of up to 28 MS/m can be achieved, the thermal conductivity is then 190 (W/K m). The yield strength of such an alloy (Rpo.2) is 80-100 MPa.

The applicant's patent EP 3 235 916 B1 discloses an alloy of the AlMg4Fe2 (Castaduct-42) type, which is preferably used for crash-relevant structural components in automobile construction. The metallurgical basis of this alloy is the Al3Fe eutectic. The electric conductivity is 16-17 MS/m.

In the prior art there are aluminum alloys with high conductivity and low strength or there exist alloys with high strength and low conductivity.

SUMMARY OF THE INVENTION

One object of the invention is, that at least one disadvantage of the alloys known from the prior art is solved.

It is an object of the alloy according to the invention that the alloy has an electric conductivity, preferably of least 23 MS/m, more preferred over 30 MS/m. At the same time the alloy should provide a high strength, preferably a Rpo.2 of at least 74 MPa, more preferred over 95 MPa. Further object is providing an alloy composition with a good castability.

Further object is, to provide an alloy composition that does not require heat treatment, while still maintaining the desired strength and conductivity.

Further object is providing an alloy composition which is suitable for mechanical machining, joining or which is corrosion resistant.

At least one of the objects, mentioned above is solved by an alloy comprising, consisting essentially of, or consisting of:

The alloy according to the inventions comprises, consists essentially of, or consists of:

Iron (Fe) 0.8 to 3.0% by weight Nickel (Ni) 0.1 to 3.5% by weight Boron (B) 40 to 300 ppm Zinc (Zn) 0-5% by weight Tin (Sn) 0-5% by weight Copper (Cu) 0-3% by weight Manganese (Mn) 0-1% by weight Magnesium (Mg) 0-0.6% by weight Phosphorus(P) 0-500 ppm Silicon (Si) 0- 0.4% and 0-0.8% by weight of an element or a group of elements selected from chromium (Cr), lithium (Li), vanadium (V), titanium (Ti), calcium(Ca), molybdenum (Mo) and zirconium (Zr) and the remainder aluminum and inevitable impurities.

DETAILED DESCRIPTION

In a preferred embodiment, the iron content ranges from or lies between 1.0-2.5% by weight.

In a further preferred embodiment, the iron content ranges from or lies between 1.2-2.0% by weight.

In a further preferred embodiment, the iron content ranges from or lies between 1.4-1.9% by weight.

In a further preferred embodiment, the nickel content ranges from or lies between 0.3-3.0% by weight.

In a further preferred embodiment, the nickel content ranges from or lies between 0.8-2.0% by weight.

In a further preferred embodiment, the boron content ranges from or lies between 70-200 ppm.

In a further preferred embodiment, the boron content ranges from or lies between 100-160 ppm.

In a further preferred embodiment, the boron content ranges from or lies between 80-150 ppm.

In a further preferred embodiment, the silicon content ranges from or lies between 0-0.3% by weight silicon.

In a further preferred embodiment, the copper content ranges from or lies between 0.2-3% by weight.

In a further preferred embodiment, the copper content ranges from or lies between 1.0-3.0%.

In a further preferred embodiment, the zinc content ranges from or lies between 0-3% by weight zinc.

In a further preferred embodiment, the zinc content ranges from or lies between 0.5% to 4.0 by weight of zinc.

In a further preferred embodiment, the magnesium content ranges from or lies between 0-0.4% by weight of magnesium.

In a further preferred embodiment, the magnesium content ranges from or lies between of 0.2-0.4%.

In a further preferred embodiment, the manganese content ranges from or lies between 0-0.1% by weight.

In a further preferred embodiment, the tin content ranges from or lies between 0-2.5% by weight.

In a further preferred embodiment, the tin content ranges from or lies between 0.2-2.5% by weight.

According to a further aspect of the invention, the cast alloy is used for high pressure die-casting, preferably for high pressure die casting of rotors and stators for electric motors and heat ex-changers, cooling and heating elements in the electronics sector or in vehicle construction.

A high pressure die casted product, preferably rotors and stators for electric motors and heat exchangers, cooling and heating elements in the electronics sector or in vehicle construction are manufactured from a cast alloy according to the invention.

The castability of the alloy according to the invention is achieved by adding the alloying elements iron and nickel, whereby eutectic phases are formed (eutectic phases improve the castability of an alloy). In particular, an AlgFeNi phase should be achieved which is, according to the literature, created in the ideal ternary system with a composition of 1.75 wt % Fe and 1.25 wt % Ni. In the case of alloy variants, an Al3Fe or Al3Ni phase may also exist. The Al3Ni phase occurs with a high Ni and at the same time a low Fe content.

According to the invention, the Fe content should be high and promote the formation of AlgFeNi together with a smaller amount of Al3Fe eutectic. In this way, the tendency of the alloy to stick is reduced and the castability is improved.

All three phases AlgFeNi, Al3Fe and Al3Ni show very fine, long fibers in the micrograph and have a similar eutectic temperature (640, 650 and 655° C.). As a result, they are created almost at the same time and in almost the same place in the casting process, which can lead to a mixing of these phases. Industrially produced die-cast parts also show numerous structural defects. As a result, these three phases (AlgFeNi, Al3Fe and Al3Ni) are often difficult to distinguish in the micrograph.

As long as no further element is added, the alloy according to the invention hardly reacts to heat treatments. Heat treatment can have a positive effect on electric conductivity and thermal conductivity. The metallurgical background is mostly an agglomeration of additional elements and a coarsening of the phases, which leads to a better conductivity of the Alpha-Al.

It is possible to increase the strength of the alloy by adding further alloy elements.

Basically a solid solution strengthening of the alpha-Al-phase should be achieved. In general, however, such solid solution strengthening usually leads to a reduction in conductivity, which is why only certain elements are even considered.

The Si content should not exceed 0.4% in order to ensure Si-free eutectics. Up to this level, only an enrichment in the alpha-Al phase is to be expected, which can slightly increase the strength. The addition of boron of around 40-300 ppm leads to a slight increase in conductivity. The metallurgical background is the formation of borides, which can reduce the negative effects of impurities. On one hand such borides can be put out during a degassing and the other hand they lead to an agglomeration of impurities and thus lead to higher conductivity (electric and thermal conductivity).

An element for increasing strength is Mg. It does not form phases with Fe, has a high solubility in Alpha-Al and however, has a negative effect on conductivity (electric and thermal conductivity). In addition, MgNi-containing phases can be formed, which interfere with the formation of an AlgFeNi phase. The alloy according to the invention should therefore either be Mg-free or contain only a small proportion of Mg, preferably maximum 0.6%.

If Si is present in the alloy, a Mg2Si phase (or one of its metastable variants) is formed, which increases strength. Further a heat treatment becomes possible.

It is known that Zn increases the strength of the alloy according to the invention and its negative effect on conductivity (electric and thermal) is limited. Without the addition of Mg, however, no significant increase in strength could be achieved. If both Mg and Zn are added, the material hardens and the strength increases.

Another element in aluminum which increases strength is the element Cu. Its negative effect on conductivity is less than that of Mg. However, a significant increase in strength could only be achieved with Cu by adding a small amount of Mg.

Further elements which may have a strength-increasing effect are Sn, Mn, Cr, Li, V, Ti, Ca, Ga, Bi, Mo and Zr.

WORKING AND COMPARATIVE EXAMPLES

In the following tables, different compositions of the alloy according to the invention and three prior art alloys, AlMg4Fe2, AlSigSr and Rotor Al 99.7 are shown. The data are in % by weight (or ppm). Values for Zn of 0.01 or 0.02% or even below can be considered as composition free of Zn. Values for Si of 0.03 or 0.04% or even below can be considered as a composition fee of Si.

For the high pressure die-cast samples (C to E, I and J, P, R to T, V to Z), the mechanical parameters (Rm, Rpo.2, A5) and the electric conductivity were measured on high pressure die casted plates with a thickness of 3 mm plates The average value from at least 6 tensile tests or 5 electric conductivity measurements is shown in Table 2.

As comparative samples, Variants I and J, both alloys known from the prior art named Castaduct-42 and Castasil-21 respectively, are shown. Variant T is a further known alloy named Rotors-Al99.7.

Variants K to O refer to gravity die casting (GDC). The measuring results with respect to mechanical parameters UTS (ultimate tensile strength), YS (yield strength) and E (A5 elongation at break) have been measured by using a Diez molds with a diameter of 16 mm. The electric conductivity was measured on separately cast and machined samples. The average value from at least 5 tensile tests or 2 conductivity measurements is shown in Table 3.

TABLE i Casting method Fe Ni Si Mg Cu Zn Variant C HP-DC 1.29 0.56 0.03 0.00 0.00 0.02 Variant D HP-DC 1.67 1.54 0.04 0.00 0.00 0.00 Variant E HP-DC 1.11 1.90 0.03 0.00 0.00 0.01 Variant I: State of the art HP-DC 1.63 0.00 0.04 4.24 0.00 0.00 Variant J: State of the art HP-DC 0.50 0.01 9.24 0.00 0.00 0.02 Variant K G-DC 0.93 0.97 0.03 0.00 0.00 0.01 Variant L G-DC 1.69 0.96 0.03 0.00 0.00 0.01 Variant M G-DC 1.70 1.21 0.03 0.00 0.00 0.00 Variant N G-DC 1.68 1.26 0.03 0.00 0.00 0.97 Variant O G-DC 1.77 1.49 0.03 0.29 0.00 3.39 Variant P HP-DC 1.67 1.55 0.04 0.00 0.00 0.00 Variant R HP-DC 1.73 1.18 0.03 0.00 0.00 0.01 Variant S HP-DC 1.80 1.43 0.03 0.31 0.00 3.50 Variant T: State of the art HP-DC 0.25 0.00 0.20 0.00 0.00 0.00 Variant V HP-DC 1.80 1.40 0.03 0.00 0.00 0.00 Variant W HP-DC 1.80 1.45 0.03 0.35 1.00 0.00 Variant X HP-DC 1.80 1.45 0.03 o.35 2.00 0.00 Variant Y HP-DC 1.80 1.47 0.03 0.00 1.00 3.47 Variant Z HP-DC 1.78 1.41 0.03 0.00 0.00 0.01 Mn Sn B Ti P Variant C 0.01 0.00 60 ppm 20 ppm 2 ppm Variant D 0.01 0.00 20 ppm 170 ppm  6 ppm Variant E 0.00 0.00 50 ppm 100 ppm  1 ppm Variant F: State of the art 0.01 0.00  2 ppm 40 ppm 3 ppm Variant J: State of the art 0.00 0.00 100 ppm   2 ppm 4 ppm Sr 0.013 Variant K 0.00 0.45 100 ppm  27 ppm 1 ppm Variant L 0.00 0.99 95 ppm 28 ppm 1 ppm Variant M 0.00 0.00 118 ppm  44 ppm 1 ppm Variant N 0.00 0.00 99 ppm 28 ppm 1 ppm Variant O 0.00 0.00 104 ppm  32 ppm 1 ppm Variant P 0.01 0.00 20 ppm 170 ppm  6 ppm Variant R 0.00 0.00 52 ppm  3 ppm 0 ppm Variant S 0.00 0.00 50 ppm 10 ppm 0 ppm Variant T: State of the art 0.00 0.00  1 ppm 100 ppm  1 ppm Variant V 0.00 0.00 71 ppm 40 ppm 1 ppm Variant W 0.00 0.00 84 ppm 50 ppm 0 ppm Variant X 0.00 0.00 84 ppm 50 ppm 0 ppm Variant Y 0.00 0.00 72 ppm 40 ppm 0 ppm Variant Z 0.00 0.00 80 ppm 40 ppm 0 ppm

Results Achieved

High Pressure Die Casting (HPC), Status F

TABLE 2 Electric Conductivity UTS [MPa] YS [MPa] E [%] [MS/m] Variant C 135 74 22,4 30,8 Variant D 161 83 15,0 28,5 Variant E 156 79 17,9 30,1 State of the art 251 122 14,4 16,3 State of the art 204 80 10,5 24,5 Variant P 161 83 15,0 29,1 Variant R 158 82 18,0 29,9 Variant S 201 94 11,9 24,5 State of the art (Ro- 100 30 20,0 35,5 Variant V 165 86 15,5 29,4 Variant W 227 103 11,9 25,4 Variant X 253 123  9,3 23,6 Variant Y 199 85 13,9 27,1 Variant Z 162 78 16,8 26,5

Gravity Die Casting (GDC), Status F

TABLE 3 Electric UTS [MPa] YS [MPa] E [%] Conductivity Variant K 100 55 26,0 33,2 Variant L 110 57 21,5 31,7 Variant M 129 63 18,4 32,4 Variant N 129 62 21,9 30,8 Variant 0 169 72  7,8 25,4 

1. A cast alloy based on aluminum-iron-nickel, comprising: iron 0.8 to 3.0% by weight nickel 0.1 to 3.5% by weight boron 40 to 300 ppm zinc 0-5% by weight tin 0-5% by weight copper 0-3% by weight manganese 0-1% by weight magnesium 0-0.6% by weight phosphorus 0-500 ppm Silicon 0- 0.4%

and 0-0.8% by weight of an element or a group of elements selected from chromium, lithium, vanadium, titanium, calcium, molybdenum and zirconium and the remainder aluminum and inevitable impurities.
 2. The cast alloy according to claim 1, wherein iron is 1.0-2.5% by weight.
 3. The cast alloy according to claim 1, wherein iron is 1.2-2.0% by weight.
 4. The cast alloy according to claim 1, wherein iron is 1.4-1.9% by weight.
 5. The cast alloy according to claim 1, wherein nickel is 0.3-3.0% by weight.
 6. The cast alloy according to claim 1, wherein nickel is 0.8-2.0% by weight.
 7. The cast alloy according to claim 1, wherein boron is 70-200 ppm.
 8. The cast alloy according to claim 1, wherein boron is 100-160 ppm.
 9. The cast alloy according to claim 1, wherein silicon is 0-0.3% by weight.
 10. The cast alloy according to claim 1, wherein copper is 0.2-3% by weight of copper.
 11. The cast alloy according claim 1, wherein copper is 1.0-3.0%.
 12. The cast alloy according to claim 1, wherein zinc is 0-3% by weight.
 13. The cast alloy according to claim 1, wherein zinc is 0.5-4.0% by weight.
 14. The cast alloy according to claim 1, wherein magnesium is 0-0.4% by weight
 15. The cast alloy according to claim 1, wherein magnesium is 0.2-0.4% by weight.
 16. The cast alloy according to claim 1, wherein manganese is 0-0.1% by weight.
 17. The cast alloy according to claim 1, wherein tin is 0-2.5% by weight.
 18. The cast alloy according to claim 1, wherein tin is 0.2-2.5% by weight.
 19. A cast alloy based on aluminum-iron-nickel, consisting of: iron 0.8 to 3.0% by weight nickel 0.1 to 3.5% by weight boron 40 to 300 ppm zinc 0-5% by weight tin 0-5% by weight copper 0-3% by weight manganese 0-1% by weight magnesium 0-0.6% by weight phosphorus 0-500 ppm Silicon 0-0.4%

and 0-0.8% by weight of an element or a group of elements selected from chromium, lithium, vanadium, titanium, calcium, molybdenum and zirconium and the remainder aluminum and inevitable impurities.
 20. A method of making a product comprising die-casting the alloy of claim 1 to form the product.
 21. The method according to claim 20, wherein the product is a rotor, a stator, a cooling element or a heating element.
 22. A high pressure die casted product comprising a cast alloy according to claim
 1. 23. The product according to claim 22, wherein the product is a rotor, a stator, a cooling element or a heating element. 